In process automation technology, one works with many different sensors. Thus, there are sensors, which sense fill level, conductivity, pressure, temperature, angular setting (e.g. on a machine) or pHvalue, as well as applications such as optical sensors, e.g. turbidity sensors or absorption sensors. Also ionsensitive sensors are applied, which sense, among other things, the nitrate content of a liquid. Each sensor is connected, in such applications, to an interface, which, in turn, is connected with a processor, which evaluates and further processes the sensor signals. In a field device, in which the processor and other active electronics are arranged, there are, most often, a number of plugin locations present, wherein, in each case, one sensor is connectable to one plugin location. Thus, also a plurality of sensors can be connected to a field device and supplied by such with electrical energy.
The field device can, however, only implement a limited consumption of electrical energy, since the energy consumption within the field device leads to a power loss in the electrical assemblies and components, which is given off as heat. Since the hermetically sealed field device can only give off a certain amount of heat to the environment, the heat remaining in the field device leads to an impermissible temperature rise of the assemblies. This can progress so far that assemblies are destroyed by the temperature rise and the field device becomes non functional.